Method and apparatus for the transmission and reception multicarrier high definition television signal

ABSTRACT

A method and apparatus for generating a multi-carrier high-definition television (HDTV) signal including a digital sound and sync (DSS) component, on a conventional television channel, for example, 6 Hz. MAC derived signal components are quadrature modulated on a plurality of subcarriers and combined in frequency multiplexed form to create an RF signal.

This application is a continuation-in-part of U.S. patent applicationSer. No. 252,954, filed Oct. 3, 1988.

CROSS REFERENCE TO RELATED APPLICATIONS AND PATENTS

1. U.S. Pat. No. 4,694,338, issued Sept. 15, 1987;

2. U.S. Pat. No. 4,794,447, issued Dec. 27, 1988;

3. U.S patent application Ser. No. 246,490, filed Sept. 19, 1988;

4. U.S. patent application Ser. No. 077,557, filed July 24, 1987;

5. U.S. patent application Ser. No. 252,954, filed Oct. 3, 1988;

6. U.S. patent application Ser. No. 271,136, filed Nov. 14, 1988; and

7. U.S. patent application Ser. No. 353,353, filed May 17, 1989.

The above-referenced patents and applications are all assigned to thesame assignee, have common inventorship, and are specificallyincorporated by reference herein.

BACKGROUND OF THE INVENTION

The invention comprises a method and apparatus for generating amulti-carrier high definition television (HDTV) signal including adigital sound and sync (DSS) signal. The invention incorporates basebandand RF processing necessary to reduce the bandwidth of an HDTV sourcesignal to that of a conventional television signal, for example 6 MHz atRF. The inventive signal format will be referred to herein as"HDS/NA-6". The baseband HDTV source signal may be 525 lines, 1:1progressive scanning or 1050 lines, 2:1 interlaced scanning.

Any system for transmitting HDTV will have to initially co-exist withconventional television receivers. Proposed systems to provide suchcompatibility fall mainly into two categories: "augmentation" systemsand "simulcast" systems. Both of these systems seek to take maximumadvantage of the existing broadcasting spectrum and at the same timeprovide both HDTV service for appropriately equipped receivers, andconventional television broadcast service, for example NTSC, forexisting television receivers.

U.S. Pat. No. 4,694,338 cited above, as well as pending applications forexample, U.S. patent application Ser. Nos. 239,096; 239,091; and239,148, all filed on Aug. 31, 1988 and owned by the present assignee,relate to methods for providing an HDTV transmission system using the"augmentation" methodology. In such "augmentation" systems, aconventional television signal is transmitted on one conventionaltelevision channel. On an adjacent channel, which can be a so-called"taboo" channel, an "augmentation" signal is transmitted which, whencombined with the conventional signal in an appropriate receiver, willprovide an HDTV display.

The so called "simulcast" systems for providing compatible HDTV serviceutilize one conventional television channel to transmit a non-compatibleHDTV television signal and an adjacent television channel to transmit aconventional television signal which can provide the same programming("simulcast") as the HDTV signal. Although this method requires the useof two conventional television channels to provide one "compatible"program (HDTV and conventional versions), the degree to which programsare "simulcast" will probably diminish as the number of HDTV receiversincreases in proportion to the total number of receivers. The televisionspectrum therefore can be gradually converted to HDTV signals asconventional television receivers are replaced with HDTV receivers.Although proposals have been made for such "simulcast" systems, forexample the Zenith "Spectrum" system and the NHK "MUSE-6" system, up tonow, a practical and efficient system for placing a true HDTV signal(one having for example a 16:9 aspect ratio, a horizontal resolution ofabout 500 TVL/ph and a vertical resolution of about 680 TVL/ph, withminimal motion artifacts) on a conventional broadcast, cable orrecording channel did not exist. An object of the instant invention isto provide such a system.

It is another object of the invention to provide a system fortransmitting an HDTV signal which can evolve naturally and economicallyfrom the existing conventional broadcasting standards.

SUMMARY OF THE INVENTION

As described in U.S. patent application Ser. No. 077,557; filed July 24,1987 and incorporated by reference herein, multiple televisioncomponents can be derived from an HDTV source signal and multiplexed intime to form the HDMAC-60 "super line" structure described therein. Theline time of the "super line" is 127.11 microseconds which is equal tofour sequential HDTV lines or two NTSC interlaced lines. As taught inthe '557 application, the components can be for example:

Y1, which is a packet for transmitting a low resolution luminance signalfor a first TV line;

Y3, which is a packet for transmitting a high resolution luminancepacket for a third TV line;

U1, which is a packet for transmitting the chroma difference of thefirst TV line;

V3, which is a packet for transmitting the V chroma difference componentof the third line;

LD2, which is a packet for transmitting a line difference signal whichcan be derived for example by the formula LD=B-(A+C)/2, where B is avalue of a pixel at a particular line and A and C are correspondingpixels vertically above and below pixel B respectively;

LD4, which is a packet for transmitting a second line difference signalderived in a manner similar to that of LD2; and

a DSS packet for transmitting digital sync, clamp period and "CD"quality digital audio.

The HDMAC-60 signal provides 131.25 "super lines" for each TV field. Ofthose "super lines", approximately 120 are active lines. Four luminancepackets are provided for each "super line" thereby creating thecapability for the transmission of high definition television (either a525 line; 1:1 progressive or a 1050 line; 2:1 interlaced) substantiallyfree of motion artifacts. The baseband video signal processingtechniques taught in the '557 application creates a luminance andchrominance frequency response footprint resembling a "stair step" withall components close to the vertical and horizontal spatial axes updatedfor example at 59.95 Hz. The details of the HDMAC-60 signal, itsderivation and the equipment needed to encode, decode and process aredescribed in the '557 application, which is specifically incorporated byreference herein.

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 254,954, filed Oct. 3, 1988, incorporated byreference herein. The '954 application describes a method and apparatusfor converting the HDMAC-60 signal into an amplitude modulated RFsignal. The present invention builds upon the teachings of the '954application to provide for the creation and transmission of an HDTVmulti-carrier signal on a channel having a conventional bandwidth.

The invention is particularly suitable for terrestrial and cable AMbroadcast environments. Because direct compatibility with conventionalreceivers is not necessary, carriers may be suppressed and standard syncheadroom may be eliminated. In addition, due to the use of heavyexpansion of the signal components derived during the encoding process,performance similar to the signal-to-noise ratio of a conventionalbroadcast signal can be obtained with a significant reduction in carrierlevel. This will enable the system to utilize the "taboo" channelseffectively without possible interchannel interference.

The method of the invention comprises the steps of modulating two signalcomponents and expanding them in time so that both signals occupy, afterexpansion, the same bandwidth taken up by only one of them beforeexpansion. If modulated in quadrature with each other, Double Side Bandor Vestigial Side Band AM signals can be used with the efficiency ofSingle Side Band AM modulation. The only way to transmit the same amountof video information in the same frequency space without expansion andquadrature modulation is to transmit the signal components in timemultiplex (one line after another) and modulated as a Single Side Bandsignal. This would be quite unpractical however because of the cost andperformance of Single Side Band RF filters. The expansion of videocomponents has the additional benefit of suppressing the ghosts added toany terrestrial video transmission.

The nature of the inventive system allows for a future increase inpermissible channel bandwidth and the associated improvement in systemperformance, simply by widening the system and channel filters. Nochange in system packaging would be required. In addition, the exactbandwidths of the listed components may be altered by selectingdifferent carrier frequencies to be described, allowing flexibility insystem performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 describes transmission format of the HDS/NA-6 signal;

FIG. 2 describes a preferred embodiment of an encoder in accordance withthe invention;

FIG. 3 describes a preferred embodiment of a decoder in accordance withthe invention;

FIGS. 4 and 5 describe the structure of a super block.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 describes the packaging of the HDS/NA-6 signal. In accordancewith the invention these components are derived from a HDTV source inputhaving a line sequence of lines 1, 2, 3, 4 and includes, for example:

Y1n--a narrow bandwidth luminance line which comprises for example, upto 215 TVL/ph (7.3 MHz), similar in nature to the HDMAC-60 Y1 line;

Y3w--a wideband luminance line which comprises for example, up to 495TVL/ph (16.8 MHz), similar in nature to the HDMAC-60 Y3 line;

LD2, LD4--line difference signals which comprise for example, up to 88TVL/ph (3 MHz), similar in nature to the HDMAC-60 LD lines;

U1n--a 4:1 vertically-decimated narrow bandwidth chrominance(color-difference) line comprising for example, 62 TVL/ph, similar innature to the HDMAC-60 U1 line; V3w--a 4:1 vertically-decimated widebandchrominance (color-difference) line comprising for example, 109 TVL/ph,similar in nature to the HDMAC-60 V3 line; and

DSS--digital synchronization, clamp and digital stereo sound, nominally0.22 MHz wide continuously.

Note that chrominance is vertically decimated 4:1, but as described inthe '557 application, the decimated may be controlled as to providealternating wideband V and U for example, from field-to-field.

All video components are expanded by the factor 27/5. The linedifference signals, LD2 and LD4, are modulated in quadrature andinterleaved with both luminance lines Y1n and Y3w, much the waychrominance is frequency interleaved in NTSC but with a much smallerinterleaving penalty due to the low-energy nature of LD and its spectralcomposition as vertical detail. Interleaving quadrature modulated LD inboth luminance lines creates a redundancy for better recovery, however,LD need only be combined with one of the luminance lines. Also, LD2 andLD4 do not have to be quadrature modulated with each other, for exampleLD2 may be interleaved with Y1n and LD4 interleaved with Y3w.

Because the luminance lines are vertically decimated, frequencyinterleaving is accomplished by selecting a carrier frequency that is anodd multiple of half the decimated line rate. This suppressed carrier,fc1, is thus (2n+1)fh/2, where fh in this embodiment is half the inputscan frequency rate. By changing the value of fc1, the listed bandwidthsof LD2 and LD4 may be altered at the expense of more channel bandwidthor effectively lower interleaving frequencies. Lowering the interleavingfrequency however may damage the low frequency spectra of allcomponents. Note that it is also possible to select a differentinterleaving frequency for the Y3w wideband component as compared to theY1n narrowband component, at the expense of receiver complexity andadditional artifacts introduced to the relatively fragilevertically-decimated high frequency luminance information carried in theupper horizontal frequencies of Y3w.

The double sideband (DSB) narrowband chrominance signal U1n is modulatedin quadrature with the narrowband luminance signal Y1n (which now hasthe imbedded, interleaved quadrature modulated LD components) which isfiltered as a vestigial sideband signal (VSB) on suppressed carrier fc2.Similarly, components Y3w and V3w are quadrature modulated on suppressedcarrier fc3, with Y3w filtered as a VSB. Note that although both Y1n andY3w vestiges face each other in this embodiment, they do not have to.However, this orientation allows the outer edges of the spectrum to growif more bandwidth is available, without altering the format, carriers,or receiver VSB Nyquist slope filter.

Digital sync and sound supported by the system is frequency multiplexedinto for example 0.25 MHz. Dolby Adaptive Delta Modulation (ADM) reducesa stereo pair to 440 kilobits per second. Using QPSK, this can beencoded into for example, about 0.22 MHz. More aggressive coding and RFtechniques could greatly increase the data capacity of the 0.25 MHzfrequency slot.

The expansion factor of 27/5 for all video components allows for asatisfactory time and frequency budget. The time budget is structured sothat all but 46 microseconds in the vertical interval are completelyoccupied with video information in any given field. The 4-line videoinformation "superblocks" total 118 for a field, thus forcing each blockto occupy about 141 microseconds (as opposed to the previous 127.11microsecond "superline" described in the '557 application). Each"superblock" consists of about 140.4 microseconds of active videoinformation, and about 0.6 microseconds for clamp and other requiredtiming information. The structure of each "superblock" is summarized inFIGS. 4 and 5.

FIG. 2 describes an embodiment of an encoder for generating an HDTVsignal in accordance with the invention.

Matrix 5 converts an HDTV RGB source signal to a luminance (Y) componentand two chrominance components (V and U). Analog lowpass filters 7, 9and 11 are anti-aliasing filters which limit Y to nominally about 16.8MHz, V to nominally about 3.7 MHz, and U to nominally about 2.1 MHzrespectively before analog to digital conversion (ADC) of the componentsby A/D converters 13, 15 and 17 respectively.

Luminance

The luminance component (Y) at the output of A/D 13 is fed into twopaths simultaneously. In a first path, a two-dimensional bandstop filter19 filters Y to suppress strong diagonal spatial information present inthe source signal. Y is then vertically decimated 2:1 in decimator 21forming in this example Y1 and Y3 (luminance components for lines 1 and3). All system control signals (e.g. for controlling decimators 21, 29,45 and 46) are generated by a vertical sequence controller 23, which canbe a timing window generator locked to input composite sync from thesource. With a 525/1:1 input, the 2:1 decimation is performed interlacestyle as described in the '557 application.

The second luminance path at the output of A/D 13 provides for thegeneration and processing of line difference components which are inthis example, LD2 and LD4. Horizontal lowpass filter 23 limits Y tonominally 3 MHz in preparation for the LD generation block 25. LD isgenerated by vertically highpass filtering Y using a vertical filter 27with an impulse response of, for example, -1/4:1/2:-1/4. The signal isvertically decimated 2:1 in decimator 29 as controlled by the verticalsequence controller 23 to be out of phase with the main luminance pathvertical decimator 21.

After first delaying LD2 by two source lines in delay 31, so that LD2will be coincident in time with LD4 at the quadrature modulator input,LD2 and LD4 are modulated in quadrature modulator 33, which multipliesLD2 by the sine of the modulating frequency and LD4 by the cosine of themodulating frequency. The modulating frequency, fc1', could be an oddmultiple of half the source line rate. All carrier frequencies and syncsignals are generated by the sync, clock, and subcarrier generator 35,which is locked to the input composite sync and controlled by thevertical sequence controller 23.

The quadrature modulated LD2 and LD4 signals are then bandpass filteredin bandpass filter 37 to remove one of the modulated images, a knownrequirement of heterodyning, and then are combined with the luminancecomponents Y1 and Y3 in adder 39. It is assumed that the quadraturemodulated LD components and the Y components are properly time-alignedto allow for optimum time utilization and to maximize the correlationeffects. The Y and the quadrature modulated LD components are frequencyinterleaved in much the same manner as chrominance is frequencyinterleaved with luminance in NTSC.

Chrominance

After conversion to digital in A/D converters 15 and 17 the chrominancecomponents, V and U pass through vertical lowpass filters 41 which limittheir vertical spatial frequencies. Two dimensional bandstop filters 43are used to suppress strong diagonal information that may causeexcessive aliasing in the decoded picture. The 4:1 vertical decimator 45selects one of four narrowband chrominance (U) lines to be encoded as anarrowband line for example U1n and similarly decimator 46 selects oneof four wideband chrominance (V) lines to be encoded as a wideband linefor example V3w. The vertical sequence controller 23 determines thenature of the decimation, much the same way as described in the '557application.

The narrowband chrominance component U1n, and the luminance linecomponent Y which has quadrature modulated LD2 and LD4 interleaved inits spectrum, are then combined in quadrature modulator 47 onto carrierfc2'. It is assumed that U1n and Y are vertically and horizontallyaligned in time before the quadrature modulation process so as to allowfor efficient time utilization and allow for modulation of correlatedterms. As shown in FIG. 2 this can be accomplished by using delays 45aand 21a. The quadrature modulated components Y:U1n are then bandpassfiltered in filter 49 to remove one modulation product which alsocreates a vestigial luminance component. Bandpass filter 49 alsodetermines the bandwidth of the luminance component Y which at thispoint can be Y1 or Y3.

In an analogous manner, the wideband chrominance component V3w, and theluminance line component Y which also has LD2 and LD4 frequencyinterleaved, are then combined in quadrature modulator 51 onto carrierfc3'. Memory 37a is used to allow the LD2 and LD4 signals to be combinedwith both Y1 and Y3 components. It is assumed that V3w and Y arevertically and horizontally aligned as mentioned above as shown, forexample in FIG. 2 by using delays 46a and 21a. The quadrature componentsare also bandpass filtered in filter 53 to remove one modulation productwhich also creates a vestigial luminance component. Bandpass filter 53also determines the bandwidth of the luminance component Y which at thispoint can be either Y1 or Y3.

The U1n:Yn quadrature modulated components are then delayed 55 to becoincident in time with the V3w:Yw quadrature modulated components. TheU1n:Yn components modulated on fc2 are then added 57 to the V3:Y3wcomponents modulated on fc3, thus constituting a frequency multiplex ofterms. These combined components are then windowed, time expanded by27/5, and frame buffered in processing block 59 which is controlled byvertical sequence controller 23. Expansion in time reduces the frequencycomponents, essentially lowering all carrier frequencies by the factor5/27. Thus, fc2=(5/27) fc2", and fc3=(5/27)fc3". Windowing is requiredto select the appropriate point in time when the desired frequencymultiplex package is properly assembled. Although in this example, bothY1 and Y3 are quadrature modulated with both chrominance components (U1nand V3w), forming U1n: Y1n, U1n: Y3n, V3w: Y1w and V3w: Y3w, thebandwidth limitation of a conventional T.V. channel, e.g. 6 mHz,requires that processor 59 provide the necessary windowing to select thedesired components, e.g. U1n: Y1n and V3w: Y3w, coincident in time, andfrequency multiplexed. Processor 59 also provides frame buffering whichis required due to the 4-input line output block packaging which exceedsthe 4-source line input period, but does not exceed the total budget ofa given field.

Audio and Sync

An audio stereo pair are input to a Dolby adaptive delta modulationencoder 61. Sync is used as a reference for a pseudo-random sequencegenerator 65 which is used in conjunction with the direct sequenceencoder 63. The resulting DSS package is quadrature phase shift key(QPSK) encoded 67 onto carrier fc4 and then bandpass filtered 69.

The modulated video and audio components are then frequency multiplexedby combining them in adder 70 in the frequency domain. Delay bufferingis implied to compensate for video/audio skew occurring in thevideo/audio paths. The video/DSS frequency multiplexed package may thenbe converted to analog by the digital to analog converter 71, bandpassfiltered 72 to remove repeat spectra, and then heterodyned 73 ontochannel fm which is conventional television broadcast, cable orrecording channel having, for example, a bandwidth of 6 mHz. The channelbandpass filter 75 removes one modulating product thereby determiningthe upper bandwidth bounds for luminance components Y.

FIG. 3 describes one embodiment of a decoder comprising the invention.The function of such a decoder is to extract the frequency multiplexedvideo and audio components from the signal HDS/NA-6 and provide an HDTVdisplay. This is accomplished by quadrature demodulating videocomponents Y1n: U1n, Y3w: V3w, and QPSK demodulating the DSS.

After channel filtering in bandpass filter 81 and demodulation to anintermediate frequency in adder 83, the HDS/NA-6 signal is converted todigital in A/D converter 85. The video components are then fed into ablock memory buffer 87 to adjust for the line-time overflow compensationprovided by the encoder. The buffer 87 also serves as a 5/27 timecompressor which is capable of positioning and delay equalizing thecomponents for further processing. Note that the compressors could alsobe located at the rear-end of the decoder for reduced clock speedrequirements in the signal processing blocks.

The frequency-multiplexed video is broken up into Y1n: U1n and Y3w: V3wpaths by bandpass filters 89 and 91 respectively which `window out` infrequency the appropriate components. Each video path comprises aquadrature demodulator (93 and 95) which quadrature demodulatesrespective chrominance components to baseband, and respective luminancecomponents (with imbedded frequency interleaved quadrature modulatedLDs) to an intermediate frequency. The baseband chrominance terms arelowpass filtered in filter 88 and 90 to remove the higher-orderdemodulation products. The luminance components are Nyquist slopefiltered in filters 97 and 99, heterodyned to baseband in mixer 101, andthen lowpass filtered to remove higher-order modulation products infilter 105.

The memory circuits in buffer 87 allow for correct positioning of theluminance/LD components so that they can be combined on one bus in atime multiplexed format. The Y1n: LD path and Y3w: LD path can then bepositioned properly in the time domain for downstream display utilizingthe delay equalizer 109, allowing the components to be multiplexed 111onto one bus. The luminance/LD components output from multiplexer 111pass to a Y/LD separator 113 which uses a bandpass filter to `windowout` in frequency the LD components. In this embodiment, with LD2 andLD4 modulated in quadrature and interleaved with both Y1n and Y3w, theluminance path 116 can be fed directly from multiplexer 111 without LDseparation because the interleaved LD alternates from line to line andthus integrates out over the picture, in much the same way that NTSCcolor is manifested on black and white receivers.

The separated LD components are then input to a quadrature demodulator115 which quadrature demodulates the LD2: LD4 components to baseband.LD4 is delayed in delay 117 for correct reconstruction positioning, andLD2 and LD4 are then combined onto one bus in time multiplexed fashion.

The luminance separated in branch 116 is comprised of Y1n: 0: Y3w: 0.The Y3w signal is one of four source lines, and its high frequenciesmust be up-interpolated. This is performed in block 119, as described inthe '557 application. The high frequencies are those above Y1n cutoff.Note that the frequencies from DC to Y1n cutoff are present in one ofevery two source lines, and these are up-interpolated (`line-doubled`)in block 120 as described in the '557 application. Y1n and Y3w are thencombined in adder 121 and further combined with the LD components inadder 122 to reconstitute the characteristic "stairstep" frequencyresponse described in the '557 application.

The chrominance signals (U1n and V3w) are present in one out of everyfour source lines, and must be up-interpolated 1: 4 in interpolators 125and 127 respectively, as described for U and V components in the '557application. The luminance (Y) and chrominance (U and V) components arethen passed through delay equalizer 123, converted to analog in D/Aconverter 125, lowpass filtered in filter 126, and then matrixed inmatrix 127 to RGB for HDTV display.

Digital audio is extracted by windowing out in frequency the DSScomponents with bandpass filter 130, and then feeding the DSS signal toa QPSK demodulator 131. This signal can then be direct sequence decoded135 under control of the pseudo-random sequence generator 133, and thenDolby ADM decoded 137.

All carrier frequencies are recovered, and the system timing and clocksare generated by control blocks 139, 141 and 143.

Although the present invention has been described in a specificembodiment, it is not to be limited thereto. Many variations will occurto one skilled in the art and these are intended to be encompassed inthe following claims.

We claim:
 1. A method for forming a frequency multiplexed televisionsignal, comprising the steps of:(a) deriving from a first televisionsignal, a pair of luminance signals, and a pair of chrominance signals;(b) quadrature modulating a first luminance signal with a firstchrominance signal on a first subcarrier forming a first frequencypacket; (c) quadrature modulating a second luminance signal with asecond chrominance signal on a second subcarrier forming a secondfrequency packet; (d) time expanding each of said frequency packets; and(e) combining said time expanded frequency packets to generate saidfrequency multiplexed television signal.
 2. The method of claim 1further comprising the steps of:(a) deriving from said first televisionsignal, a pair of line difference signals; (b) combining at least one ofsaid line difference signals with at least one of said luminancesignals.
 3. The method of claim 2 wherein said line difference signalsare quadrature modulated with each other on a third subcarrier forming athird frequency packet which is then combined with one of said luminancecomponents.
 4. The method of claim 3 wherein said third frequency packetis combined with both of said luminance components.
 5. Apparatus forforming a frequency multiplexed television signal, comprising:a) meansfor deriving from a first television signal a pair of luminance signalsand a pair of chrominance signals; b) first modulating means coupled tosaid deriving means, for quadrature modulating a first luminance signalwith a first chrominance signal on a first subcarrier so as to form afirst frequency packet; c) second modulating means coupled to saidderiving means, for quadrature modulating a second luminance signal witha second chrominance signal on a second subcarrier so as to form asecond frequency packet; d) means coupled to said first and secondmodulating means, for expanding each of said frequency packets; and e)means coupled to expanding means, for combining said expanded frequencypackets to generate said frequency multiplexed television signal.
 6. Theapparatus of claim 5, further comprising:a) second deriving means forderiving from said first television signal, a pair of line differencesignals; b) means coupled to said second deriving means, for combiningone of said line difference signals with at least one of said luminancesignals.
 7. The apparatus of claim 6, further comprising means coupledto said second deriving means, for quadrature modulating said linedifference signals with each other on a third subcarrier so as to form athird frequency packet.
 8. Apparatus for providing a television displayfrom the frequency multiplexed signal of claim 5, comprising incombination:a) means for deriving from said frequency multiplexed signalsaid first and second frequency packets; b) means for deriving from saidfirst frequency packet, said first luminance signal and said firstchrominance signal; c) means for deriving from said second frequencypacket, said second luminance signal and said second chrominance signal;and d) means for combining said first and second luminance componentsand said first and second chrominance components to form said televisiondisplay.